import 'dart:async';
import 'dart:core';
import 'dart:io';

import 'package:flutter/foundation.dart';
import 'package:logging/logging.dart';
import 'package:photo_manager/photo_manager.dart';
import 'package:photos/db/file_updation_db.dart';
import 'package:photos/db/files_db.dart';
import 'package:photos/utils/file_uploader_util.dart';
import 'package:shared_preferences/shared_preferences.dart';

// LocalFileUpdateService tracks all the potential local file IDs which have
// changed/modified on the device and needed to be uploaded again.
class LocalFileUpdateService {
  FilesDB _filesDB;
  FileUpdationDB _fileUpdationDB;
  SharedPreferences _prefs;
  Logger _logger;
  static const isLocationMigrationComplete = "fm_isLocationMigrationComplete";
  static const isLocalImportDone = "fm_IsLocalImportDone";
  Completer<void> _existingMigration;

  LocalFileUpdateService._privateConstructor() {
    _logger = Logger((LocalFileUpdateService).toString());
    _filesDB = FilesDB.instance;
    _fileUpdationDB = FileUpdationDB.instance;
  }

  Future<void> init() async {
    _prefs = await SharedPreferences.getInstance();
  }

  static LocalFileUpdateService instance =
      LocalFileUpdateService._privateConstructor();

  Future<bool> _markLocationMigrationAsCompleted() async {
    _logger.info('marking migration as completed');
    return _prefs.setBool(isLocationMigrationComplete, true);
  }

  bool isLocationMigrationCompleted() {
    return _prefs.get(isLocationMigrationComplete) ?? false;
  }

  Future<void> markUpdatedFilesForReUpload() async {
    if (_existingMigration != null) {
      _logger.info("migration is already in progress, skipping");
      return _existingMigration.future;
    }
    _existingMigration = Completer<void>();
    try {
      if (!isLocationMigrationCompleted() && Platform.isAndroid) {
        _logger.info("start migration for missing location");
        await _runMigrationForFilesWithMissingLocation();
      }
      await _markFilesWhichAreActuallyUpdated();
      _existingMigration.complete();
      _existingMigration = null;
    } catch (e, s) {
      _logger.severe('failed to perform migration', e, s);
      _existingMigration.complete();
      _existingMigration = null;
    }
  }

  // This method analyses all of local files for which the file
  // modification/update time was changed. It checks if the existing fileHash
  // is different from the hash of uploaded file. If fileHash are different,
  // then it marks the file for file update.
  Future<void> _markFilesWhichAreActuallyUpdated() async {
    final sTime = DateTime.now().microsecondsSinceEpoch;
    bool hasData = true;
    const int limitInBatch = 100;
    while (hasData) {
      var localIDsToProcess =
          await _fileUpdationDB.getLocalIDsForPotentialReUpload(
        limitInBatch,
        FileUpdationDB.modificationTimeUpdated,
      );
      if (localIDsToProcess.isEmpty) {
        hasData = false;
      } else {
        await _checkAndMarkFilesWithDifferentHashForFileUpdate(
          localIDsToProcess,
        );
      }
    }
    final eTime = DateTime.now().microsecondsSinceEpoch;
    final d = Duration(microseconds: eTime - sTime);
    _logger.info(
      '_markFilesWhichAreActuallyUpdated migration completed in ${d.inSeconds.toString()} seconds',
    );
  }

  Future<void> _checkAndMarkFilesWithDifferentHashForFileUpdate(
    List<String> localIDsToProcess,
  ) async {
    _logger.info("files to process ${localIDsToProcess.length} for reupload");
    var localFiles = await FilesDB.instance.getLocalFiles(localIDsToProcess);
    Set<String> processedIDs = {};
    for (var file in localFiles) {
      if (processedIDs.contains(file.localID)) {
        continue;
      }
      MediaUploadData uploadData;
      try {
        uploadData = await getUploadDataFromEnteFile(file);
        if (file.hash != null ||
            (file.hash == uploadData.fileHash ||
                file.hash == uploadData.zipHash)) {
          _logger.info("Skip file update as hash matched ${file.tag()}");
        } else {
          _logger.info(
            "Marking for file update as hash did not match ${file.tag()}",
          );
          await FilesDB.instance.updateUploadedFile(
            file.localID,
            file.title,
            file.location,
            file.creationTime,
            file.modificationTime,
            null,
          );
        }
        processedIDs.add(file.localID);
      } catch (e) {
        _logger.severe("Failed to get file uploadData", e);
      } finally {
        // delete the file from app's internal cache if it was copied to app
        // for upload. Shared Media should only be cleared when the upload
        // succeeds.
        if (Platform.isIOS &&
            uploadData != null &&
            uploadData.sourceFile != null) {
          await uploadData.sourceFile.delete();
        }
      }
    }
    debugPrint("Deleting files ${processedIDs.length}");
    await _fileUpdationDB.deleteByLocalIDs(
      processedIDs.toList(),
      FileUpdationDB.modificationTimeUpdated,
    );
  }

  Future<void> _runMigrationForFilesWithMissingLocation() async {
    if (!Platform.isAndroid) {
      return;
    }
    // migration only needs to run if Android API Level is 29 or higher
    final int version = int.parse(await PhotoManager.systemVersion());
    bool isMigrationRequired = version >= 29;
    if (isMigrationRequired) {
      await _importLocalFilesForMigration();
      final sTime = DateTime.now().microsecondsSinceEpoch;
      bool hasData = true;
      const int limitInBatch = 100;
      while (hasData) {
        var localIDsToProcess =
            await _fileUpdationDB.getLocalIDsForPotentialReUpload(
          limitInBatch,
          FileUpdationDB.missingLocation,
        );
        if (localIDsToProcess.isEmpty) {
          hasData = false;
        } else {
          await _checkAndMarkFilesWithLocationForReUpload(localIDsToProcess);
        }
      }
      final eTime = DateTime.now().microsecondsSinceEpoch;
      final d = Duration(microseconds: eTime - sTime);
      _logger.info(
        'filesWithMissingLocation migration completed in ${d.inSeconds.toString()} seconds',
      );
    }
    await _markLocationMigrationAsCompleted();
  }

  Future<void> _checkAndMarkFilesWithLocationForReUpload(
    List<String> localIDsToProcess,
  ) async {
    _logger.info("files to process ${localIDsToProcess.length}");
    var localIDsWithLocation = <String>[];
    for (var localID in localIDsToProcess) {
      bool hasLocation = false;
      try {
        var assetEntity = await AssetEntity.fromId(localID);
        if (assetEntity == null) {
          continue;
        }
        var latLng = await assetEntity.latlngAsync();
        if ((latLng.longitude ?? 0.0) != 0.0 ||
            (latLng.longitude ?? 0.0) != 0.0) {
          _logger.finest(
            'found lat/long ${latLng.longitude}/${latLng.longitude} for  ${assetEntity.title} ${assetEntity.relativePath} with id : $localID',
          );
          hasLocation = true;
        }
      } catch (e, s) {
        _logger.severe('failed to get asset entity with id $localID', e, s);
      }
      if (hasLocation) {
        localIDsWithLocation.add(localID);
      }
    }
    _logger.info('marking ${localIDsWithLocation.length} files for re-upload');
    await _filesDB.markForReUploadIfLocationMissing(localIDsWithLocation);
    await _fileUpdationDB.deleteByLocalIDs(
      localIDsToProcess,
      FileUpdationDB.missingLocation,
    );
  }

  Future<void> _importLocalFilesForMigration() async {
    if (_prefs.containsKey(isLocalImportDone)) {
      return;
    }
    final sTime = DateTime.now().microsecondsSinceEpoch;
    _logger.info('importing files without location info');
    var fileLocalIDs = await _filesDB.getLocalFilesBackedUpWithoutLocation();
    await _fileUpdationDB.insertMultiple(
      fileLocalIDs,
      FileUpdationDB.missingLocation,
    );
    final eTime = DateTime.now().microsecondsSinceEpoch;
    final d = Duration(microseconds: eTime - sTime);
    _logger.info(
      'importing completed, total files count ${fileLocalIDs.length} and took ${d.inSeconds.toString()} seconds',
    );
    await _prefs.setBool(isLocalImportDone, true);
  }
}